The present invention relates to a proximity switch operating in noncontact fashion with a dc circuit arrangement lying between the input section and the sensor field generator, with the circuit arrangement being divided into a main part arranged in a basic housing on the terminal side, and into a sensor part exhibiting the sensor field generator.
German Pat. No. 2,817,020 discloses a proximity switch wherein the sensor part is accommodated in a square or cubic component that can be threaded or plugged onto the square or cylindrical main part in a rotatable fashion or in various positions. It is thereby possible to align the response side of the sensor part in correspondence with the approach direction of the object to be monitored without having to reposition the main part of the proximity switch, also called power block. Thereby, the aligned mounting of the proximity switch at machines or the like is facilitated especially in case of cramped space conditions. However, in this arrangement, the main part must also be attached in the closest proximity to the monitoring site at machines or the like, and for this reason an appropriate amount of space must there be available; however, this is not realizable in all cases. Since the main part is frequently supplied with mains voltage, whereas the sensor part is operated only with low-voltage current, the mains voltage is carried up to the monitoring site which can give rise to safety problems.
The invention is based on the object of providing a proximity switch usable even under very much restricted installation conditions at the measuring and/or monitoring site, which switch can be mounted in a simple way and wherein the sensor part, operated with a weak current, is protected in a particularly reliable fashion against the supply voltage, e.g. mains voltage, of the main part.
In order to attain this object, the invention provides a plug-in adapter exhibiting a plug-in socket for the sensor part which latter is equipped with a plug-in cable, an ac/dc converter with a core coil connected in front thereof being arranged in this adapter, and the latter being associated with a dc/ac converter located in the basic housing of the main part and having a core coil connected thereafter, the core coils lying in each case behind the mounting sides of basic housing and plug-in adapter and transmitting, by inductive coupling, the energy from the main part to the connected sensor part and the signals from the sensor part to the main part.
A number of advantages are attained by the invention. On the one hand, a complete electric separation is achieved between, on the one hand, the main part and, on the other hand, the plug-in adapter and the sensor part which latter thus can be installed, with the use of a plug-in cable of appropriate length, at a remote distance from the monitoring point. Since the plug-in adapter is likewise attached to the main part, the sensor part, in this case containing merely the sensor coil and electronic components required for sensor field generation and signal evaluation, can be made of a very compact size so that it can be still accommodated even in case of very cramped space conditions. The plug-in connection between sensor part and plug-in adapter facilitates mounting since in this case sensor parts can be utilized having correspondingly long plug-in cables and, if necessary, also extension cables, and anyway the sensor part can be exchanged for another one in an extremely simple way. A further advantage of the invention resides in the fact that the main part can also be used as a module of an only bipartite proximity switch wherein the other module forming the sensor part and having a cube shape, for example, is equipped with a corresponding ac/dc converter and can be connected to the main part in placed of the plug-in adapter. Even in such a case, there still exists a complete electrical separation between the two modules.
Advantageously, according to the present invention, the housing of the plug-in adapter includes a base plate attachable to the basic housing and a truncated cone integrally formed at the rear side of the base plate and surrounding the plug-in socket. The plug-in socket and plug of the plug-in cable are fashioned as connector plugs that can be threaded together.
Furthermore, advantageously, according to the present invention, a plug-in adapter includes a smoothing capacitor connected after the ac/dc converter.
Additionally, the basic housing of the main part is provided, according to the present invention, at a mounting side thereof, with a dovetail hookup recess. The plug-in adapter includes a square head on its mounting side, with the square head being undercut on all sides and insertable in the dovetail hookup recess.
Moreover, according to the present invention, an open end of the dovetail hook-up recess may be closed by a pressure member extending over the square head of the plug-in adapter and can be attached by threading.
The subject matter of the present invention will be described in greater detail below with reference to the accompanying drawings.